The portreserve program aims to help services with well-known ports that lie in
the bindresvport() range. It prevents portmap (or other programs using
bindresvport()) from occupying a real service's port by occupying it itself,
until the real service tells it to release the port (generally in its init
script).
This utility originated in this discussion:
https://bugzilla.redhat.com/show_bug.cgi?id=103401